Video codec: Chapter two digital video

1. Image and Video

• Image: is a material reproduction of human perception of vision;
• Three-dimensional natural scene objects include: depth, texture and luminance information;
• Two-dimensional images: texture and luminance information

• Video: Continuous Images
• Video consists of a number of images, including the object's motion information, also known as motion image.

2. Digital video

Digital Video: A digital sampling representation of the natural scene space and time.

• Spatial sampling: Resolution (Resolution)
• Spatial sampling: Frame Rate/sec

3. Spatial sampling

• Two-dimensional digital video image sampling

4. Digital Video System

• Acquisition: Camera, Camera
• Processing: codecs, transmission devices
• Display: Display

5. Human visual system Hvs

• HVS: eyes, nerves, brain
• Hvs Features:

Insensitive to high frequency information

More sensitive to High contrast

More sensitive to luminance information than chroma information

More sensitive to movement information

6. The design of the digital video system should consider the features of Hvs:

• Discard high frequency information, value code low frequency information
• Improving the subjective quality of edge information
• Reduce the resolution of Chroma
• Special handling of areas of interest (region of Interesting,roi)

7. RGB color Space

• Three primary colors: red, green and blue
• Any color can be produced by a certain mixture of three primary colors
• RGB Chroma Space

Made up of RGB three colors

Widely used in bmp,tiff,ppm, etc.

Each chroma ingredient is usually expressed in 8bit [0,255]

8. YUV Color Space

The mainstream encoding and decoding standard compression objects are YUV images

10. Common YUV Image format

• Defines the image format based on the luminance resolution of the YUV image

  Format	Brightness resolution
  Sqcif	128x96
  QCIF	176x144
  Cif	352x288
  4CIF	704x576
  Sd	720x576
  HD	1280x720 1920x1080

11. Frame and field images

• A frame image consists of two fields--the top field, the bottom field

12. Progressive and interlaced images

• Progressive Image: Two fields of a frame image are obtained at the same time, Ttop=tbot
• Interlaced Image: Two fields of a frame image are obtained at different times, Ttop≠tbot

13. Video Quality evaluation

• Lossy video compression makes codec images different, and it needs a means to evaluate the quality of decoded images.
• Quality Evaluation: Objective quality evaluation, subjective quality evaluation, objective evaluation of video quality based on vision

Objective Quality Evaluation:

• Advantages: quantifiable, repeatable measurement results, simple measurement
• Cons: not fully compliant with the person's supervisor perception

14. Methods of objective evaluation

The method of objective evaluation commonly used:

Video codec: Chapter two digital video